1. Field of Invention
Various exemplary embodiments relate generally to a method of manufacturing a semiconductor memory device, and more particularly, to a method of manufacturing a three-dimensional memory device.
2. Description of Related Art
To manufacture high-capacity lightweight semiconductor memory devices, degrees of integration are being increased. Three-dimensional semiconductor memory devices are being developed to achieve a higher degree of integration. In a three-dimensional semiconductor memory device, memory cells coupled to word lines are stacked in a vertical direction from a substrate. Thus, as the number of word lines increases, the height or thickness of the memory cell stack, in which the word lines and insulating layers filled between the word lines are stacked, may also be increased.
When the height of the stacked structure including the word lines and the insulating layers increases, a difference in width of a hole or a trench may occur during a dry etch process of forming the hole or the trench in the stacked structure. For example, since the dry etch process is performed in a direction from top to bottom, the hole or the trench formed in the upper part of the stacked structure may be over-etched compared with the hole or the trench is formed in the lower part of the stacked structure. The difference in width along the height of the trench may lead to differences in electrical characteristics, causing degradation in reliability of semiconductor memory devices.